In certain situations, operation of aircraft at high altitude can require restarting operation of an aircraft propulsor. For example, certain aircraft propulsors can be an internal combustion engine that can include one or more turbochargers powered by energy from the exhaust of the internal combustion engine. As the air at high altitude is thin, the internal combustion engine can fail to provide enough airflow and power to both restart the internal combustion engine and spool the turbocharger.